Agriculture Reference
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in panicle exsertion in any of the stages and duration of cold
exposure, as this was the most sensitive stage to cold when cold
tolerance was measured as the reduction of spikelet fertility.
In all durations of cold exposure and stages, indica genotypes
were more sensitive than japonica in considering percentage
reduction in spikelet fertility (Cruz et al. 2006).
Cold treatment at the young microspore stage results in a
dramatic depletion of starch accumulation in the pollen grains
at anthesis. Starch is essential in pollen grains, as storage
carbohydrate for energy supply during pollen germination
and fertilization.
Measurements of sucrose content showed that sucrose
levels increased in anthers that were cold-treated at the young
microspore stage. Consistent with these results, it was found
that the enzyme activity levels of cell wall invertase, but not
soluble invertase decreases upon cold treatment at the young
microspore stage only.
These results further suggest that cold induces a reduction
of cell wall invertase activity, which then leads to a blockage
of sucrose supply to developing pollen grains. This blockage
is explained by the absence of starch synthesis in the pollen
grains at maturity (Fig. 23).
Reduction of cell
wall invertase
activity
Increase of
sucrose in pollen
grain at anthesis
Cold stress at
young micro-
sporogenesis
Pollen grain
abortion
Depletion of
starch in pollen
grain
Fig. 23
Effects of low temperature on pollen grain.
